This invention relates to abrasive blasting with particulate material, and relates more particularly but not exclusively to systems and equipment for abrasive blasting, and to sub-systems and apparatus therefor.
2. Description of the Prior Art
The cleaning of surfaces by abrasive blasting is a well known procedure, involving the hurling of particulate material against the surface either by mechanical means, or by entraining the particulate material in a jet of air directed at the surface. The particulate material is more or less abrasive, and may be in the form of metal shot, sand or any other suitable material. The particulate material may be coarse (e.g. gravel-like), fine (e.g. a powder), or smooth (e.g. beads). The impact of the particulate abrasive material on the surface to be cleaned tends to abrade and remove surface contamination (e.g. dirt), and may even remove part of the surface itself.
Practical advantages of abrasive blasting as a surface cleaning process have led to attempted extension of the process to cleaning of surfaces previously cleaned by other methods, or which were left uncleaned. However, abrasive blasting systems which are good at cleaning the surfaces of metal castings (for example) may prove unsuitable for cleaning more delicate surfaces, such as mediaeval stonework. Success in the application of abrasive blasting to cleaning or otherwise treating surfaces presenting special problems requires care in selection of abrasive material, its feed rate, transport velocity and other parameters defining the abrasive process. Reduction or elimination of the possibility of operator error is also highly desirable, that is it should ideally be difficult or impossible for the operator to use the abrasive cleaning equipment in a manner which (for example) results in unnecessary damage to the surface being cleaned, and in excessive consumption of abrasive material.